1. Field of the Invention
The present invention relates to an iterated image transformation and decoding apparatus and method, and a recording medium. More particularly, the present invention relates to an iterated image transformation and decoding apparatus and method which, by using iterated transformation, decodes a coded bit stream output from a coder for an image which is provided to a system which performs low-rate-coding of an image, or efficient transmission or storage of an image, and a recording medium.
2. Description of the Related Art
As a typical conventional image compression method, a commonly called JPEG (Joint Photographic Coding Experts Group) method standardized by the ISO is known. This JPEG method uses DCT (Discrete Cosine Transform), and when a relatively high bit rate is assigned, provides a satisfactory coded/decoded image. However, if the number of coding bits is reduced to some degree, block distortion which is characteristic of the DCT become conspicuous, and image degradation becomes noticeable.
In addition to this, recently, an image compression method using an iterated function system (IFS) is beginning to attract attention. This method utilizes self-similarity of an image under the precondition that when a part of an image is taken out from the entire image, another image which closely resembles the taken-out image is present in the form of a different size within the image. In this iterated function system, the block distortion such as that of the above-described JPEG is not conspicuous, and the self-similarity among the blocks of different sizes within the image is utilized, yielding the advantage that there is no dependence upon the resolution during decoding. This iterated transformation coding is also called fractal coding, and applications to various fields are expected.
The basic construction of the above-described iterated transformation coding is shown in, for example, xe2x80x9cImage coding based on a fractal theory of Iterated Contractive Image Transformationsxe2x80x9d by Arnaud E. Jacquin, IEEE Transactions on Image Processing, Vol.1, No.1, pp.18-30. The iterated transformation and coding apparatus shown herein is shown in FIG. 9, and the iterated transformation and decoding apparatus shown herein is shown in FIG. 10.
The iterated transformation and coding apparatus will be described first with reference to FIG. 9.
An original image 300 supplied to this iterated transformation and coding apparatus of FIG. 9 is input to a block generation circuit 200 where it is divided into a plurality of blocks 301. These blocks are set so as not to overlap each other. Also, reduced images 307 obtained by reducing the original image 300 by a reduced-image generation circuit 202 are stored in a reduced-image storing circuit 204. For the divided blocks 301, in an approximation area search circuit 201, reduced images are searched in a full search within the reduced-image storing circuit 204 and the most closely resembling reduced image is detected from among the reduced images. Approximation block position information 306, obtained hereby, indicating which portion of the reduced image should be extracted, is transmitted to the reduced image storing circuit 204, and a reduced image 305 of a specified area is taken out. Then, the reduced image 305 of the specified area is subjected to, for example, rotation/reverse/level-value conversion in accordance with a transformation parameter 304 in a rotation/reverse/level-value conversion section 203, and a reduced image 303 after being transformed is output. As a result, the transformation parameter 304 and the approximation block position information 306 are output as an iterated function system (IFS) code 302.
Next, a description will be given of the iterated transformation and decoding apparatus with reference to FIG. 10.
The IFS code 302 output from the iterated transformation and coding apparatus of FIG. 9 is once input to an IFS code storing circuit 205 and stored therein. The IFS code 302 is read therefrom sequentially in block units for a plurality of times. An IFS code reading circuit 206 reads an IFS code 308 in block units and separates it into the approximation block position information 306 and the transformation parameter 304. Then, the approximation block position information 306 is input to a reduced-image storing circuit 210, and the reduced image 305 of the specified area is taken out from the reduced image in accordance with the position information 306. This reduced image 305 of the specified area is subjected to a transformation process based on the transformation parameter 304 by the rotation/reverse/level-value conversion section 203, is added and copied onto the decoded image within a decoded-image storing circuit 208 and is stored. When the IFS code reading circuit 206 completes the reading of the IFS code 308 of all the blocks, the IFS code reading circuit 206 sends a reading completion notification signal 310 to a copying control circuit 207. This copying control circuit 207 measures the number of times a series of the above copying process has been performed. When the number does not reach a preset value, a re-reading instruction signal 309 is output to the IFS code reading circuit 206, and the copying process is performed again on all the blocks of the image. At the same time, re-processing instruction information is sent in accordance with a decoded-image output control signal 311, and a decoded image 313 is connected, by a switch 209, to an input 314 with respect to the reduced-image generation circuit 202. The reduced-image generation circuit 202 generates a reduced image 315 in exactly the same manner as on the coder side, and the contents of the image stored in the reduced-image storing circuit 204 are replaced with this image. When, on the other hand, the copying process has reached a fixed number of times, the copying control circuit 207 issues a termination instruction in accordance with a decoded-image output control signal 311, the decoded image 313 is connected to a final output image 316 by a switch 209, and an output of the decoder is obtained.
In an example of conventional technology such as that described above, the approximation with respect to an image obtained by performing a reduction and transformation process on a block at an arbitrary place of the self entire image screen is measured. The position information of the most closely resembling block and the transformation parameter at that time are selected from all possible candidates. As a result, in the coder, a coded code is written into the bit stream in the sequence of the coded block.
Meanwhile, in the decoder, the coded bit stream is unscrambled, and a decoded image having the same size or the same aspect ratio as that of the input image on the coder side is output. However, in a texture mapping process (pasting of texture) for a three-dimensional shape, often used recently in CG (computer graphics), etc., three-dimensional shapes can take various forms and therefore, it is necessary to match the image with the shape.
In such a case, conventionally, the common practice is that by performing a filtering process, etc. on an image which is decoded once again, its aspect ratio is changed. If this changing of the aspect ratio can be performed at the same time as the decoding, the texture mapping process, etc., in CG can be simplified greatly.
An object of the present invention, which has been achieved in view of such circumstances, is to provide an iterated image transformation and decoding apparatus and method, in which changing of the aspect ratio can be performed at the same time as decoding without using a filtering process or the like during decoding, and a recording medium.
To achieve the above-mentioned object, according to one aspect of the present invention, there is provided an iterated image transformation and decoding apparatus comprising: two polygon information generation means for unscrambling a coded bit stream, inputting aspect-ratio information, and reconstructing information for generating two different polygonal images; image transformation and generation means for mapping-transforming the pixel value of an image within one of the polygons and the position of the polygon; image memory means for storing the transformed polygonal image; and control means for performing control so that the mapping transformation and generation of the polygon is iteratively processed.
With such a construction, the first polygon information generation means inputs aspect-ratio information and reconstructs the position information of a polygon of a mapping transformation target. Similarly, the second polygon information generation means inputs aspect-ratio information and reconstructs the position information of a polygon of a mapping transformation source. The image transformation and generation means performs a predetermined mapping transformation process on all the pixels of a second polygonal image in order to generate a new polygonal image. The image memory means stores the transformed polygonal image. The control means controls an iteration process of a decoding loop so that a final decoded image is output.
According to another aspect of the present invention, there is provided an iterated image transformation and decoding apparatus comprising: two polygon information generation means for unscrambling a coded bit stream and reconstructing information for generating two different polygonal images; two polygon transformation and generation means for inputting polygon deformation information in order to deform and generate a polygon; image transformation and generation means for mapping-transforming the pixel value of an image within one of the deformed polygons and the position of the polygon; image memory means for storing the mapping-transformed polygonal image; and control means for performing control so that the mapping transformation and generation of the polygon is iteratively processed.
With such a construction, the first polygon information generation means unscrambles a coded bit stream and reconstructs the position information of a polygon of a mapping transformation target. The second polygon information generation means unscrambles a coded bit stream and reconstructs the position information of a polygon of a mapping transformation source. The first polygon deformation and generation means inputs polygon deformation information and deforms a first polygon in order to generate a new polygonal image. The second polygon deformation and generation means inputs polygon deformation information and deforms a second polygon in order to generate a new polygonal image.
The above and further objects, aspects and novel features of the invention will become more apparent from the following detailed description when read in connection with the accompanying drawings.